This invention relates to two-piece, three-piece and multi-component fluid center golf balls comprising one or more layers formed with compositions that provide increased resistance to water permeation while still exhibiting good ball properties. These compositions may be incorporated into the cover and/or the core of a two-piece ball, or within the cover, core, center, and/or intermediate layer of a three-piece or multi-component golf ball.
Conventional golf balls can be divided into several general types or groups: (1) one-piece balls; (2) two-piece balls; (3) wound balls; and (4) other balls with three or more layers. The difference in play characteristics resulting from these different constructions can be quite significant.
Balls having a two-piece construction are generally most popular with the average recreational golfer because they provide maximum distance. Two-piece balls commonly include a single solid core, usually formed of a crosslinked rubber. Solid cores are often formed of polybutadiene that is chemically crosslinked with zinc diacrylate and/or similar crosslinking agents. They are covered by a tough, cut-resistant blended cover, formed of a material such as SURLYN(copyright), an ionomer resin produced by E. I. Du Pont de Nemours and Co. of Wilmington, Del. The combination of the core and cover materials imparts a relatively high initial velocity to the ball which results in improved distance. Due to the relative rigidity of these materials, two-piece balls have a hard xe2x80x9cfeelxe2x80x9d when struck with a club.
At the present time, the wound ball remains the preferred ball of the more advanced players due to its spin and feel characteristics. Wound balls typically have either a solid rubber or fluid-filled center around which many yards of a stretched elastic thread or yarn are wound to form a core. The wound core is then covered with a durable cover material such as SURLYN(copyright), or a softer material, such as balata or a castable polyurethane. Wound balls are generally softer and provide more spin than the aforementioned two-piece balls. Particularly with approach shots onto the green, the high spin rate of a soft, wound ball enables the golfer to stop the ball very near its landing position.
Multi-component balls are constructed with a cover and a core, wherein the core further comprises a center and an intermediate layer disposed concentrically between the center and the cover. The intermediate layer may be constructed as a solid layer or a wound layer, where a wound layer comprises many yards of elastic thread that are stretched and wrapped around the center. The core, comprising the center and intermediate layer, is encased within a durable cover material such as a SURLYN(copyright) or another similar material, or, alternatively, within a softer cover such as balata or polyurethane. Multi-component golf balls, especially those formed with a wound intermediate layer, are generally softer than a two-piece ball and can provide more spin, enabling a skilled golfer to exert more control over the ball""s flight.
Golf ball centers incorporated within, e.g., multi-component balls may be solid or fluid-filled spheres. A variety of methods are known for forming fluid-filled centers, such as those disclosed in U.S. Pat. No. 5,836,831. The ""831 patent discloses the use of thermoplastic polymers for forming spheres used in such fluid-filled centers. In the ""831 patent, polyether-amide block copolymers are formed into hemispherical half-shells by compression or injection molding. The half-shells may be joined to form hollow spheres in a number of ways including welding, chemical bonding, RF heat sealing, induction bonding, hot wire seaming, co-injection molding or hot melt sealing. Alternatively, the center shell may be formed by extrusion blow molding, co-extrusion blow molding or injection blow molding.
The hollow center spheres are then filled with an appropriate fluid, generally an aqueous salt solution having a specific gravity of from about 1.0 to about 1.6, and preferably, about 1.25. Filling the hollow center spheres may be carried out by piercing the surface with a needle and injecting the fluid. The hole formed may be sealed in a number of ways including the application of adhesives that may be cured with heat or radiation, with solvent or water-based paints, hot melt adhesives or a polymeric material. A solid or wound layer is then applied around the fluid-filled center, using materials and methods well known in the art, to form a golf ball.
Permeation of water through one or more layers of a multi-layer golf ball may affect the properties or performance of that ball. Accordingly, one approach to obviating such water permeation has been to increase the hardness of the base polymer in the composition or blend used to form one or more golf ball layers. For example, different grades of PEBAX(copyright), a polyether-amide block copolymer, demonstrate a decrease in water vapor permeability as the hardness of the grade increases (Elf Atochem, Philadelphia, Pa., technical bulletin: PEBAX(copyright)xe2x80x94Basis of Performance, page 18). However, such prior attempts to obviate the potential problem of water permeation across a golf ball layer, involving the incorporation of such harder polymeric materials into those layers, have generally led to unfavorable changes in the physical and performance characteristics of golf balls, such as increased compression and stiffness. In addition, although such harder materials are resistant to water permeation, it has been observed that the coefficient of restitution and initial velocity are both lower in balls formed with them. This has been especially problematic with respect to such compositions when employed in the formulation of hollow spheres used for assembly of fluid-filled centers.
Accordingly, there has thus been a long-felt need for golf balls formed with layers having improved resistance to water permeation wherein the materials relied upon for such purpose are capable of substantially preventing water permeation across one or more such layers without substantially affecting the overall physical and performance characteristics of the resultant golf ball. An additional constraint is found in the requirement that these materials should, nevertheless, be amenable to contemporary processes for the production of golf balls, and, more particularly, to the formation of hollow spheres used for the construction of fluid-filled centers. The present invention admirably meets these objectives.
An object of the present invention is to provide golf balls comprising one or more layers formed with compositions having improved resistance to water permeation while maintaining or even improving the performance characteristics of such balls.
Another object of the present invention is to provide polymer blend compositions comprising hydrophilic thermoplastic polymers and hydrophobic olefinic polymers that are incorporated within one or more layers of a golf ball, such that resistance to water permeation through such layers is substantially improved.
A further object of the present invention is the formation of hollow center shells used in the manufacture of fluid-filled centers for multi-component golf balls, from the blends disclosed herein, thereby substantially preventing fluid permeation across the center shell.
A particular object of the present invention is the provision of a wound golf ball having an improved resistance to water permeation, with a polyurethane, polyurea or epoxy-urethane cover and a fluid-filled center that includes a center shell formed from a blend of a polyether-amide or a polyether-ester block copolymer and a maleic anhydride grafted metallocene-catalyzed copolymer of ethylene and octene, a maleic anhydride grafted metallocene-catalyzed copolymer of ethylene and hexene, or a maleic anhydride grafted metallocene-catalyzed copolymer of ethylene and butene.
The present invention is directed, in a first embodiment, to a golf ball comprising at least one layer having improved resistance to water permeation. In a preferred embodiment, the ball comprises a fluid-filled center, a cover and at least one intermediate layer interposed between the center and the cover. The fluid-filled center comprises a center shell formed from a composition comprising a blend of at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer. Preferably, the hydrophobic polymer is compatible with the hydrophilic thermoplastic polymer. The golf ball of the present invention is further characterized in that it has a coefficient of restitution of at least 0.75 and a compression of less than about 110. The intermediate layer may be formed of a plurality of tensioned elastomeric windings or, alternatively, one or more solid layers. Compositions used to form the center shell of the ball may comprise, for example, a blend of a polyether-amide or a polyether-ester block copolymer and a maleic anhydride grafted metallocene-catalyzed copolymer of ethylene and octene, ethylene and hexene, or ethylene and butene, or a blend of these metallocene-catalyzed copolymers.
The present invention is directed, in an alternate embodiment, to a wound golf ball comprising one or more layers having improved resistance to water permeation, which comprises a fluid-filled center, at least one layer of tensioned elastomeric windings surrounding the fluid-filled center, and a cover. In this embodiment, the fluid-filled center comprises a center shell, formed from a composition comprising a blend of a polyether-amide or polyether-ester block copolymer and a maleic anhydride grafted metallocene-catalyzed copolymer of ethylene and octene, ethylene and hexene, or ethylene and butene, or a blend of these metallocene-catalyzed copolymers. Furthermore, the golf ball of this embodiment has a coefficient of restitution of at least about 0.75 and a compression of less than about 110.
In another embodiment, the invention is directed to a golf ball having a fluid-filled center which comprises a center shell having a hardness of about 30 to about 80 Shore C, a flexural modulus of about 500 psi to about 70,000 psi and a specific gravity of about 0.8 to about 2.5. In a preferred embodiment, the center shell has a hardness of about 50 to about 65 Shore C, a flexural modulus of about 3000 psi to about 20,000 psi and a specific gravity of about 1.3 to about 2.0, or more preferably from about 1.5 to about 1.9.
In a further embodiment, the invention is directed to a golf ball having a cover formed from a polyurethane composition, an example of which is disclosed in U.S. Pat. No. 5,334,673 which is incorporated herein by reference. The polyurethane composition may comprise at least one polyurethane prepolymer formed from 4,4xe2x80x2-diphenyl methane diisocyanate, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-biphenyl diisocyanate, or para-phenylene diisocyanate, and a polyol that is cured with a polyamine selected from the group consisting of 3,5-dimethylthio-2,4-toluenediamine; 3,5-dimethylthio-2,4-toluenediamine; 3,5-dimethylthio-2,6-toluenediamine; N,Nxe2x80x2-dialkyl diamino diphenyl methane; trimethylene glycol-di-p-aminobenzoate; polytetramethyleneoxide-di-p-aminobenzoate and mixtures thereof. The polyol may be selected from the group consisting of polytetramethylene ether glycol; poly(oxypropylene) glycol; polybutadiene glycol; 1,4-butanediol initiated caprolactone; diethylene glycol initiated caprolactone; trimethylol propane initiated caprolactone; neopentyl glycol initiated caprolactone; polyethylene adipate glycol; polyethylene propylene adipate glycol; and polybutylene adipate glycol.
In another embodiment, the invention is directed to a golf ball having a cover formed from a polyurea-based composition, for example as disclosed in U.S. Pat. No. 5,484,870, which is incorporated herein by reference, or an epoxy-urethane-based composition as disclosed in U.S. Pat. No. 5,908,358, which is incorporated herein by reference. In still further embodiments of the present invention, the golf ball cover may be formed from thermoset and thermoplastic compositions.
More generally, the present invention is directed toward golf balls comprising one or more layers having improved resistance to water permeation. Disclosed herein are blends of hydrophilic thermoplastic polymers and hydrophobic, olefinically-based polymeric materials, which are advantageously used in the construction of such layers to provide a reduction in the permeation of water through those layers.
In a further embodiment, the present invention is directed toward golf balls, incorporating the above-identified blends into the cover, into an intermediate layer disposed concentrically between the cover and the center and/or into the core, to improve resistance of the golf ball to water permeation by rendering these golf ball portions substantially resistant to permeation by water. It should be understood, moreover, that any or all of the cover, intermediate layer and/or core may comprise a plurality of layers.
Center shells, used in the formation of golf balls with fluid-filled centers, represent a preferred use for the blends of the present invention but, as noted above, these blends may be incorporated within substantially any layers(s) within the ball. Wound balls, for example, constructed with fluid-filled centers employing these polymer blends not only provide the same or superior play characteristics, but also provide improved resistance to water permeation, as compared to wound balls using hydrophilic polymer based fluid-filled center cores. It is also contemplated that fluid-filled centers of the present invention are useful in non-wound or xe2x80x9csolidxe2x80x9d golf balls, which comprise one or more layers of a solid material molded around a fluid-filled center core.
In one embodiment, the golf ball includes a cover and a core wherein either or both of the core and the cover may comprise a plurality of layers, with at least one of the layers comprising a blend of at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer. Preferably, the hydrophobic polymer is compatible with the hydrophilic thermoplastic polymer.
In a more specific embodiment, the hydrophilic thermoplastic polymer is a homopolymer, copolymer, terpolymer, block copolymer, grafted polymer, or some mixture of these. Similarly, the hydrophobic material may be selected from among a homopolymer, copolymer, terpolymer, block copolymer, grafted polymer, or a mixture thereof.
In a further embodiment, the hydrophilic thermoplastic polymer is selected from the group consisting of polyether-ester block copolymers, polyester-ester block copolymers, polyether-amide block copolymers, polyester-amide block copolymers, thermoplastic urethanes, and blends thereof. Similarly, the hydrophobic polymer may be selected from the group consisting of ethylene-glycidyl acrylate copolymers, ethylene-glycidyl methacrylate copolymers, maleic anhydride grafted metallocene-catalyzed copolymers of ethylene and octene, maleic anhydride grafted metallocene-catalyzed copolymers of ethylene and hexene, maleic anhydride grafted metallocene-catalyzed copolymers of ethylene and butene, ethylene-n-butyl-acrylate-glycidyl acrylate terpolymers, ethylene-n-butyl-acrylate-glycidyl methacrylate terpolymers, ethylene-methyl acrylate-glycidyl acrylate terpolymers, ethylene-methyl acrylate-glycidyl methacrylate terpolymers, ethylene-n-butyl acrylate-methacrylic acid based ionomers, ethylene-n-butyl acrylate-acrylic acid based ionomers, and mixtures thereof.
In one embodiment, the hydrophilic thermoplastic polymer is a polyether-amide or polyether-ester block copolymer, and the hydrophobic polymer is a maleic anhydride grafted metallocene-catalyzed copolymer of ethylene and octene, ethylene and hexene, or ethylene and butene, or a copolymer of ethylene-n-alkylacryalte-glycidyl acrylate or ethylene-n-alkylacryalte-glycidyl methacrylate.
The thermoplastic hydrophilic polymer may comprise, by weight, 99% to 1%, preferably 95% to 5%, and more preferably, 90% to 10% of the polymeric components of the blend. The at least one hydrophobic polymer may comprise, by weight, 1% to 99%, preferably 5% to 95%, and more preferably, 10% to 90% of the polymeric components of the blend. Optionally, the composition may include additional compatibilizers, density adjusting fillers, including metals and foaming agents.
The invention is also directed to a method for forming a golf ball with improved resistance to water permeation, comprising the steps of forming a golf ball core from a mixture comprising a blend of at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer and encasing that core in a cover to provide a golf ball. In a further embodiment of this method, the cover is formed of a mixture that comprises at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer, and which is used to encase a core, wherein the core may also comprise such a blend.
The invention is further directed to methods for forming multi-component golf balls with improved resistance to water permeation, comprising the steps of forming a golf ball center, covering the center in an intermediate layer to form a core, and encasing the core in a cover to provide a golf ball, wherein the center, core and cover may all comprise more than one layer, any of which may be formed from a mixture comprising a blend of at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer.
In a further embodiment, the invention is directed to a method for forming multi-component golf balls with improved resistance to water permeation, comprising the steps of forming a golf ball center, covering the center in a first intermediate layer to form a core, forming a second intermediate layer over the core and encasing the so-covered core in a cover to provide a golf ball, wherein at least one of the intermediate layers may be formed from a mixture comprising a blend of at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer. Any of the cover, intermediate layer or the core may comprise more than one layer, and any of the layers comprising the intermediate layer may comprise a blend of at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer.
This invention is also directed toward a method of making a golf ball having improved resistance to water permeation comprising the steps of forming a blend comprising at least one hydrophilic thermoplastic polymer and at least one hydrophobic polymer, forming a hollow center shell from the blend, filling the hollow center shell with a fluid, thereby providing a fluid-filled center, wrapping the fluid-filled center with an elastic thread, thereby providing a wound core, and encasing the wound core in a cover, thereby providing a golf ball having improved resistance to water permeation.